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Note 5 - Related-party Transactions (Details Textual)				1 Months Ended	6 Months Ended		67 Months Ended
Note 5 - Related-party Transactions (Details Textual)	Sep. 18, 2018 USD ($)	Sep. 08, 2016	Dec. 01, 2014 USD ($)	Nov. 30, 2017 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Aug. 01, 2018 USD ($)	Dec. 31, 2018 USD ($)
Insurance Premium Refund Receivable					$ 150,000
Affinity Returns from SAS and SBS [Member]
Estimated Litigation Liability								$ 901,000
NMS [Member]
Percent of Reimbursement					1.00%
Merhold Property Trust [Member]
Number Of Vehicles Subleased					20
Number Of Vehicles Leased					172
Lessee, Operating Lease, Term of Contract					4 years
SGRP Holdings [Member] \| SPAR BSMT Joint Venture [Member]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage		51.00%
JKC [Member] \| SPAR BSMT Joint Venture [Member]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage		39.00%
EILLC [Member] \| SPAR BSMT Joint Venture [Member]
Variable Interest Entity, Qualitative or Quantitative Information, Ownership Percentage		10.00%
EILLC [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					10.00%
NMS [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					49.00%
NSRS [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					100.00%
Resource Plus, Inc [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					49.00%
RJ Holdings [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					50.00%
FRIEDSHELF 401 Proprietary Limited [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					23.00%
Lindicom Proprietary Limited [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					26.00%
SPAR Todopromo [Member]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners					49.00%
SBS [Member]
Number of Merchandising Specialists					4,500
Withheld Final Mark-up Compensation Due to Related Party			$ 112,000
Additional Funding for Field Specialist Payments			$ 13,000
Payments for Cash Collateral Deposits, Allocated to Related Party							$ 379,000
SBS [Member] \| Post-termination Expenses [Member]
Loss Contingency, Estimate of Possible Loss					$ 200,000
SBS [Member] \| Domestic Merchandising Specialists Field Force [Member]
Payments for Related Party Services					$ 13,300,000
Percent Of Service Provided By Related Party					43.00%
SBS [Member] \| Cost Plus Fees [Member]
Related Party Transaction, Rate			2.96%
SAS [Member]
Number of National, Regional, and District Administrators						57
Payments for Cash Collateral Deposits							965,000
SAS [Member] \| Domestic Field Management [Member]
Payments for Related Party Services						$ 2,300,000
Percent Of Service Provided By Related Party						91.00%
SAS [Member] \| Advances for Affinity Insurance Plan [Member]
Related Party Transaction, Amounts of Transaction					$ 226,000
SPAR InfoTech, Inc. [Member] \| Alleged Lost Tax Benefits and Other Expenses [Member]
Loss Contingency, Damages Sought, Value	$ 190,000
SPAR InfoTech, Inc. [Member] \| Allegedly Owed Programming Services [Member]
Loss Contingency, Damages Sought, Value	$ 900,000
NMS [Member]
Majority Interest Ownership Percentage By Parent					51.00%
Resource Plus, Inc [Member]
Majority Interest Ownership Percentage By Parent					51.00%
Meridian [Member]
Majority Interest Ownership Percentage By Parent					51.00%
Mr. Mason [Member] \| Merhold Property Trust [Member]
Related Party Ownership Percentage					50.00%
Mr. Mason and Mr. Bristow [Member] \| Merhold Cape Property Trust [Member]
Related Party Ownership Percentage					50.00%
SPAR Todopromo [Member]
Majority Interest Ownership Percentage By Parent					51.00%
Mr. Juan F. Medina Domenzain [Member] \| CON [Member]
Related Party Ownership Percentage					90.00%
SPAR Marketing Force [Member]
Payments for Cash Collateral Deposits, Allocated to Related Party							296,000
All Others [Member]
Payments for Cash Collateral Deposits, Allocated to Related Party							$ 290,000
Robert G. Brown and William H. Bartels [Member]
Related Party Ownership Percentage				59.00%
SBS And SAS [Member]
Reserve for Related-party Receivables, Amount Recorded During Period				$ 901,000
Reserve for Related-party Receivables, Amount Recorded During Period, Cash Collateral				675,000
Reserve for Related-party Receivables, Amount Recorded During Period, Insurance Premium Advance				$ 226,000